The present invention relates to a focus controlling method of a laser beam within an optical disk apparatus for recording/reproducing the optical disk, and in particular, relates to the focus controlling technology of a laser beam for an optical disk, for achieving a stable focus drawing-in with reducing ill influences due to a stray light.
An optical disk apparatus is widely used for enabling an access to a large amount of data at high speed, using an optical disk, i.e., a large-capacitive and low-cost optical information recording medium, but without contact thereon within a personal computer, for example. However, in such an optical disk apparatus, a reflection light entering into an inside of an optical pickup, which is generated when a focus point of the laser beam is coincident with the optical disk surface, comes to be stray lights after being scattered therein, and due to such the stray lights is generated an alias or false signal, other than a focus signal generated due to reflection upon a recording surface of the optical disk.
In recent years, the optical disk apparatus becomes more compact. As such, Work Distance (WD) of the optical pickup comes to be narrow, and further a next-generation DVD (so-called Blu Disc (BD (®)) is put into a practical use thereof, which is very narrow in this WD. Accompanying with this, the optical disk surface and a focus lens come close to each other, and for that reason, the ill influences of the stray lights as mentioned above become more pronounced and cannot be ignored.
Herein, as the conventional art for removing the ill influences of the imitation signal due to the stray lights, Japanese Patent Laid 0pen No. 2002-367193 discloses therein a control in which a position of generating the false signals due to the stray lights is memorized in advance duing manufacturing, and an operation of focus drawing-in will not be started within a time during when the false signals are generated.
In addition, Jananese Patent Laid Open No. 2005-174383 discloses a control of calculating out focus drive signal voltage at a position receiving no ill influence due to the surface reflection on the optical disk, upon basis of the focus drive signal voltage when detecting out so-called S-like signal, so as to move the optical pickup to that position, thereby removing an offset due to the stray lights.
However, with such the conventional arts as was mentioned above, there are still remaining the following drawbacks:
Thus, within the optical disk reproducing apparatus disclosed by JP 2002-367193, since a time for generating the false signals depends on an mount of surface deflection of the disk, it is impossible to determine uniformly. In addition thereto, in particular, with the BD disk being very narrow (for example, in a degree of 0.1 mm), in the distance between the disk surface and the recording surface thereof, as was mentioned above, the time for masking the said false signals also comes to be very narrow, and the control itself is difficult to conduct.
Also, with the later JP 2005-174383, however, in the similar manner to the above, it is difficult to apply it into a high-speed drive, which can be easily affected with the ill influences due to the surface deflection, and in particular, into a BD disk drive.
On the other hand, further for avoiding such the ill influences upon the S-like signal due to the stray lights, a method of achieving the focus drawing-in is provided while directing the focus point from a reverse side of the optical disk to a surface side thereof, for example. With such method, however, within the BD disk drive being very narrow in the WD of the optical pickup, accompanying with thin-sizing of the optical disk apparatus, there is still a possibility that the optical pickup collides on the optical disk, thereby causing damage thereupon.